Improvement in mercurial thermostats



W. B. FARRAR. Mercurial Thermostat.

No. 200,382. Patented Feb. 19,1878.

UNITED STATES PATENT OEEIGE.

WARD B. FARRAR, OF CHICAGO, ILLINOIS, ASSIGN OR TO IVESTERN ELECTRICMANUFACTURING COMPANY, OF SAME PLACE.

IMPROVEMENT IN MERCURIAL THERMOSTATS.

Specification forming part of Letters Patent N o. 200,382, datedFebruary 19, 1878; application filed August l, 1877.

.To all whom it may concern:

Be it known that I, vWARD B. FARRAR, of the city of Chicago, in thecounty of Cook and State of Illinois, have invented a new and usefulImprovement in Electric Mercurial Thermostat, which is fully describedin the following specifica-tion, reference being had to the accompanyingdrawings, in which- Fignre l represents a side elevation of a thermostatembodying my improvements, and Fig. 2 a transverse section of the saine.

My invention relates especially to thermostats which are intended to beinserted in walls or ceilings of rooms, and connected with an electricalalarm, for the purpose of producing a signal automatically ifa re occursin the room where placed.

In the drawings, A represents a glass bulb, provided with a tube, B,which is of the same construction as the mercury-bulb tube ordinarilyemployed in thermostats of this class, except in the particularshereinafter named. The tube Bis constructed with a sharp angular bend,b, a slight distance from the bulb A. The tube has the usual small borerunning through it, in the outer end of which is inserted a short pieceof line platinum wire, C. Around the inner end of the wire C the bore inthe tube B is enlarged, so as to forma small chamber, D, as shown inFig. 2 of the drawmgs.

A wire, E, is coiled a few times around the outer end of the tube B, andthe outer end 0f the platinum wire C is soldered to this coil. A similarwire, F, is coiled around the tube next to the bulb A, and to it isattached, by soldering or otherwise, the shield Gr, which is constructedof the usual form, to surround and protect the bulb of mercury. Aplatinum wire, H, is soldered-to the shield at one end, and enters themercury in the bulb at the other, in the usual manner, and aconnecting-wire, I, is also soldered to the shield, to furnish anattachment for one of the circuit-wires. The

other line or circuit wire is attached to the free end of the wire coilE, which thus furnishes a sufficiently strong attachment for theline-wire.

It will be seen that the shield is attached to Vand supported by thecoiled wire F, so that it not only has a substantial support, but alsoleaves the bulb free, the end ofthe bulb which projects through theshield not being relied upon to support the latter.

The bend in the tube B, and corresponding bend in the bore, is aneffectual stop to prevent the jumping of the mercury in the tube underthe impulse of a sudden and severe jar.

The chamber D affords space in which the mercury may accumulate when theheat is intense, and thus relieves the pressure in the bulb and tube,which would otherwise occur, and frequently cause the bursting of thebulb.

It will thus be seen that the improvements described add materially tothe strength, durability, and reliability of the thermostat, for thepurpose of giving alarms of fire.

-It is understood, of course, that the device is connected with abattery and signal apparatus in the usual well-known manner, and isinserted, as usual, in the wall or ceiling of a room.

H. ving thus described my invention, what I claim, and desire to secureby Letters Patent, 1s-

l. The wire E, coiled around the upper or outer end of the tube, formingthe connection between the line-wire and platinum wire C, substantiallyas and for the purpose set forth.

2. The wire F, coiled around the tube at the bulb end thereof, incombination with the shield attached thereto, substantially as and -forthe purpose set forth.

WARD B. FARRAR.

Witnesses L. A. BUNTING, JNO. C. MACGREGOE.

